Measurement of the efficiency of a PCR reaction. A: Estimation of the efficiency using the Serial dilution (SerDil) method. Five dilutions of a cDNA sample were amplified using the fibronectin (FN) amplicon. Each dilution was analyzed with five replicates PCR reactions and each data point represents one Ct value determined as in Figure 1B. Linear regression parameters and calculation of the efficiency value are shown in the inserted textbox. B: Screenshot of the LinReg PCR program analysis window, which allows the estimation of the efficiency value from each set of amplification curves . Data correspond to one of the reactions performed from the undiluted sample used in part A. C: Comparison of the efficiency values obtained using the Serial dilution and LinReg methods for the FN amplicon. Efficiency values were determined from four independent cDNA samples using the Serial Dilution method as in part A, or the LinReg method as in part B. For each sample, efficiency value were either determined from one linear regression performed on 24 reactions altogether (Serdil) and error bars calculated from the standard deviation on the slope as determined from the linear regression method or the individual efficiency values determined from each of the same 24 PCR reactions (LinReg) were averaged, and error bars represent the standard deviation on the set of values.